If I wanted to put online a member site, in addition to my digital downloads (purchase to own files), which I have had some good success with, what's a thin, fast and easy website template and script on the market?

I've spent months - each - building my catalog sites, and my dto sites, with my own PHP/SQL... but if I'm going to do a "member site" (trial, weekly, monthly), I'd like to use a template, and have it be fairly uncomplicated to update content, as I buy content from content providers, and travel and shoot on my own.

Thanks...